Jason Parkinson, a freelance video journalist working for Ruptly, had sent two tweets linking to Ruptly video content from the first day of the arms fair, organised by Clarion Events, that ended with the #stopDSEI hash tag.

When the crew arrived at ExCel London for the second day of the event they filmed a rooftop protestor before entering the building. After then entering the venue, Parkinson said the team were "held" in the DSEI press office for 30 minutes, before they were told the entire Ruptly team had had its press accreditation revoked for the use of the #stopdsei hashtag.

We've been kicked out of #DSEi, press credentials revoked, told it was for using the #StopDSEi hash tag on tweets linking to @Ruptly reports

"The StopDSEi hashtag was used to flag up and further promote the work of Ruptly to people who were following that specific hashtag," Parkinson told Journalism.co.uk via email. "Over this week I have been covering the convention itself and the protests surrounding the event."

Parkinson said he and his field producer believed that filming the protestor may cause problems on re-entering the event, but to be refused on the basis of a personal tweet came as a surprise. The official Ruptly Twitter account also tweeted links to the footage but did not include the #stopDSEI hashtag.

"I argued against this for about five minutes," said Parkinson, "stating how ridiculous it was to suggest I was a threat due to a hashtag, that our reporting had been objective and was available for everyone to see via the links on my Twitter feed and on the official Ruptly Twitter feed, and that they were restricting our right to report. We were then promptly asked to leave."

Parkinson said the person who asked them to leave "refused to give me his name and hid the ID card hanging round his neck".

Philip Wolmuth, chair of the London Photographers branch of the National Union of Journalists, told Journalism.co.uk that "tweeting to publicise stories and real-time coverage has become standard practice among journalists, as has the use of hashtags".

"Hashtags open up the tweet to the widest audience, it was standard practice and not out of the ordinary and interference in the freedom of the press in this way is unacceptable."

Parkinson told the Guardian today: "There has been absolutely no agenda with our reporting – it has just been us recording what is going on and what people are saying. I find it incredible that our use of hashtags to ensure our work is seen by both those opposed to and in favour of the arms fair has led us to be ejected."

A spokesperson for DSEI said: "The show organisers reserve the right to grant, reject or revoke accreditation at any time, at their discretion."

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